The invention relates to an arrangement for illumination and scanning of an object by means of a scanning disk similar to a Nipkow disk comprising a number of spirally arranged elementary openings, which arrangement is particularly suitable for microscopic investigation of living tissues.
An arrangement of this kind called "tandem scanning" has been described in the British periodical "Scanning", Vol. 7, pages 97 to 108 from July 1985, and in applicants' U.S. Pat. No. 3,517,980, incorporated herein by reference. One part of a rotating scanning disk with spirally arranged elementary openings is illuminated by an illuminating field, whereby to an elementary opening of the scanning disk a similar opening is provided diametrically with respect to the rotation axis of the scanning disk. The elementary openings illuminated by said illuminating field subsequently allow the passage of an illuminating pencil of rays reaching the object to be investigated by way of a system for light splitting and light reflected from said object is returned to the scanning disk to pass through the elementary opening of the scanning disk corresponding to the elementary opening through which the illuminating pencil of rays has passed and forms by way of an eyepiece of a microscope an image of the object.
Parts of paths of illuminating pencils of rays and of image forming pencils of rays are joining in the system for light splitting comprising also an objective of a microscope, focussed on the object to be investigated.
The system for light splitting comprises either one or a number of prisms provided with a semitransparent mirror layer or a possibly thin semitransparent mirror.
A substantial reduction of contrast is, however, experienced by application of prisms due to disturbing reflexes, so that the application of prisms has been mostly abandoned. Better results have been achieved by application of semitransparent mirrors with minute thickness which proved to have better optical properties than prisms. Negligibly thin plates have been used having excellent properties mounted on a stiff ring with a semitransparent mirror coating provided on said plate. However, technological difficulties and raw materials of variable properties caused that also this solution could not bring reliable results.